The invention relates in general to automatic telephone systems, and more particularly to a system for providing the special routing of service calls by a code translation in a private automatic branch exchange (PABX).
Prior art PABX systems generally have a number of special features associated with their operation. One of the features common to the art has been the provision for abbreviated access in connection with certain business functions.
In particular this feature has been used in hotels, motels, and similar businesses to simplify the means by which a guest may be connected to various special services provided in that facility. Generally, a list of codes corresponding to the special services which a guest may procure, such as maid service, room service, swimming pool, dining room, and others, is attached to his station.
The guest may obtain any of the services listed by dialing one of the service access codes from his station and waiting for the PABX to connect him to the corresponding special service station. Therefore, to facilitate recollection of the special service codes and the use of the services, it is important that the codes be uniform throughout the facility and as simple as possible (abbreviation to one digit is preferred).
Also, in a large complex of buildings, wherein each building may have its own special services, it is desirable to insure that a guest occupant of one building attempting to contact a special service will be automatically routed to the special service station in his building, rather than that service in another building of the complex.
To accomplish the preceding objects, one prior art common control telephone system uses dual translation circuits for connecting subscriber stations dialing service access codes to the desired service stations. The system provides a number translator circuit for marking line circuits connected to a line link network and a code translator circuit for marking trunk circuits connected to a trunk link network. The number translator circuit performs the dual function of converting dialed directory numbers into an equipment location of a line circuit as well as converting an equipment number of a line circuit into a directory number. The code translation circuit on the other hand converts central office prefixes, area code, and the special services codes into routing information for seizing a trunk marker to mark circuits connected to a trunk link network outlet. The system then provides for the connection of the subscriber station, marked by the number translator, through the line link network to a special service station on the trunk link network, marked by the code translator.
Although this system establishes special service code connections in an advantageous and reliable manner, a separate trunk circuit is needed for each special service code station. Such trunk circuits are relatively more expensive than line circuits and also take up a separate outlet on the trunk link network.
The outlets on the trunk link network generally should be reserved for common connecting circuitry such as outgoing trunks and ringing controls that may be used by all line circuits and not for terminating single special service stations. Thus, the special service stations would be more efficiently accessed if available through commonly connectable circuitry than through an expensive dedicated trunk circuit and trunk link network outlets.